1. Field of the Invention
The present invention pertains to a device for application of dope on male threads, comprising a swivel motor, the swivel motor operating a rotatable top, on said top at least one dope application nozzle being arranged.
2. Description of the Related Art
It is known to provide a series of devices for doping of threads, that is devices for application of grease on the threads at the ends of drill pipes, to facilitate the joining and disengagement of pipes in a drill string.
This work used to be performed completely by manual labour by a worker applying the grease with a brush. Due to the heavy work schedule, there is seldom time enough to clean the threads before applying the grease. The work was also high-risk because of the heavy pipes being transported over the drill floor. The drill floor is in general a dangerous working place, and a demand for reduced personnel on the drill floor exists.
There have been machines developed to facilitate the application of the dope, but the majority of these machines still require one worker to be present to operate the machine.
A device, which can be remotely operated is shown in NO 173.893, which shows a device in which the thread grease is applied on male threads, or pin end, by a brush roller. The end of the pipe is according to this device lowered onto a centering means, where after the roller shaped brush is rotated around the pipe end.
U.S. Pat. No. 2,642,034 shows a hand operated device for spraying thread grease on the female end, or the box end, of the pipe. In this case a mouthpiece with one or more nozzle is fed into the pipe end and may optionally rotate in this position.
NL 8800247 shows a hand operated device for applying thread grease on a female end.
DE 2620526 shows devices for applying thread grease on female or male ends, which also are hand operated.
DE 3537633 shows a similar device to the above, which is also hand operated.
U.S. Pat. No. 4,043,295 shows a device for application of dope on female threads. It comprises a head having a nozzle for spraying dope. The dope is bent sideways by an air jet emitted sideways from an air nozzle. The air nozzle is rotatable around the longitudinal axis of the head. The device can be hand held or remotely operated.
NO 179.920 also shows a device for application of dope on female threads. It comprises a sideways directed nozzle which is rotatable around its longitudinal axis. This device must be inserted into and removed from the female end by hand.
U.S. Pat. No. 5,653,819 shows a device for cleaning of male or female threads. The threads to be cleaned are inserted into a chamber and rotationally mounted spray nozzles inside this chamber perform a cleaning action. No application of dope is described.
U.S. Pat. No. 4,895,205 shows a device for cleaning and chemical treatment of sections of pipe. The pipe is fed through a tunnel, and non-rotational spray nozzles perform treatment of the outside of the tube. No application of dope is described.
Most of the above prior art devices are hand held devices, which require one or more persons to be present near the pipe end.
Such manual labour is both high-risk and physically heavy, and there is therefor a desire to eliminate the need for a person to be present by the pipe end to apply the thread grease.
The device according to NO 173.893 functions fairly well, but it has certain disadvantages. It has inter alia no possibility for efficient cleaning of the threads before the thread grease is applied. When a pipe end is brought into a position over the device, the pipe end must be centered quite accurately over the centering means, where after the pipe tube is lowered onto the centering means or the centering means is lifted up to the pipe end. This consumes a relatively long time, and a risk exists that the pipe end does not hit the centering means.
U.S. Pat. No. 4,043,295 and NO 179.920 can only be used for doping female threads and cannot be used for male threads.
The object of the present invention is to provide a dope application device, which functions with increased efficiency and which has a simple construction and can be used for application of dope on the male threads.
The above features are achieved by arranging the dope application nozzle at a distance from the rotational axis of the top, said distance being larger than the radius of a thread section to be doped.
It is also an object of the present invention to provide a dope application device, which cleans the threads before the application of the grease.
The dope application according to the present invention can in an easy way be placed between the pipe racks on a rig of the RamRig(copyright) type. In this way the dope can be applied just before the pipe is placed in the ramp which transports it up to the drill floor. The device can also be placed on the drill floor on a separate arm or on the so called rouchneck.